Omeprazole — Stomach Acid Medication Guide | KiwiMeds
✅ Reviewed by a Registered Pharmacist NZ | Last updated: May 2026 | This information is for educational purposes only and does not replace advice from your doctor or pharmacist.
What is omeprazole?
Omeprazole is a proton pump inhibitor (PPI) — one of the most commonly prescribed medicines for stomach problems in New Zealand. It works by significantly reducing the amount of acid your stomach produces. You may know brand names like Losec, but generic omeprazole is widely funded by Pharmac.
What is it used for? (NZ context)
Omeprazole is used to treat heartburn and acid reflux (GERD/GORD), stomach ulcers, duodenal ulcers, H. pylori infection (alongside antibiotics), damage caused by anti-inflammatory medicines (NSAIDs), and Zollinger-Ellison syndrome. It is funded by Pharmac for many of these conditions.
How does it work?
Omeprazole blocks the “proton pump” — a mechanism in the cells lining your stomach wall that releases acid. By blocking these pumps, omeprazole dramatically reduces acid production, allowing your stomach and oesophagus to heal and reducing the discomfort of acid reflux.
How to take it
Always take omeprazole exactly as directed by your doctor or pharmacist. Do not stop or change your dose without medical advice.
Common side effects
- Headache
- Nausea, stomach pain
- Diarrhoea or constipation
- Flatulence
- These are usually mild and improve with time
Serious side effects to watch for
Long-term use of PPIs (over 1 year) has been associated with: reduced magnesium levels (hypomagnesaemia), vitamin B12 deficiency, increased risk of bone fractures, and increased risk of certain gut infections (e.g. C. difficile). Talk to your doctor if you have been on omeprazole long-term.
Important drug interactions
- Clopidogrel (a blood thinner) — omeprazole may reduce its effectiveness; discuss alternatives with your doctor
- Methotrexate — omeprazole may increase its levels
- Some HIV medications
- Warfarin — may affect blood-thinning levels
NZ-specific information
Pharmac funding: Omeprazole is funded for many indications. Generic omeprazole capsules (20mg, 40mg) are available. Brand names in NZ: Losec (branded), generic omeprazole (funded). Available forms: Capsules and tablets; dispersible tablets for those who have difficulty swallowing.
Frequently asked questions
Can I take omeprazole long-term? It is meant for short-to-medium courses for most conditions. However, some people do take it long-term. Your doctor should review whether you still need it periodically. Can I take antacids with omeprazole? Yes, antacids can provide quick relief while omeprazole takes effect (it takes 1-4 days to reach full effect).
Related medications
Ibuprofen (pain/inflammation) | Amoxicillin (antibiotic) | Metformin (diabetes)
Always talk to your pharmacist or doctor for personalised advice. This information is general and educational — it does not replace a consultation with your healthcare provider.
References & Further Information
The following New Zealand and international resources were used to inform this page: